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ULN2004A: Internal Clamping Diode Characteristics

Zach Bruce
Prodigy 80 points
Part Number: ULN2004A

For UNL2004DA, would you have an Internal diode model for the clamping diode between the collector and emitter that could be used for simulations? If not, do you have the forward voltage for the low current draws (i.e. 10mA)? The datasheet has a typical of 1.7V for forward voltage but its not clear at what current this happens.

  • 0
    TI__Genius 10652 points

    Zach, 

    The spec for VF is measured at an IF of 350mA, per the datasheet, excerpt below.

    The clamp diodesare useful when driving inductive loads like solenoids. For larger inductive loads, they can not handle the energy and people may use external schottky for driving more inductive loads. The modern external diodes have the benefit of turning on sooner than the internal clamp, shunt away the energy from the IC, and are very well defined by the manufacturer ( such as through Datasheet, PSPICE models).

    Please let me know if you have further questions.

    Best

    Dimitri

  • 0 in reply to dimitri james
    Prodigy 80 points

    Thank you Dimitri. I do have an external diode on this line for protection. What I'm wanting to confirm is that my external diode will turn on before the internal clamping diode so that I can't damage the internal diode. Do you have any information about the forward voltage at lower current levels?

    Thank you,

    Zach

  • 0 in reply to Zach Bruce
    TI__Genius 10652 points

    Zach Bruce said:

    Thank you Dimitri. I do have an external diode on this line for protection. What I'm wanting to confirm is that my external diode will turn on before the internal clamping diode so that I can't damage the internal diode. Do you have any information about the forward voltage at lower current levels?

    The diode can turn on ~0.7V, so Schottky is recommended. 

    Best

    Dimitri